ia

c,

inee

43007 Tarragona, Spainb Department of Industrial Engineering, University of Pamplona, Km 1 Va Bucaramanga, Pamplona N. de S., Colombiac Group of Applied Thermal Engineering (CREVER), Department of Mechanical Engineering, University of Rovira I Virgili (URV), Av. dels Pasos Catalans 26, 43007 Tarragona, Spain

a r t i c l e i n f o

Article history:

Received 10 January 2008

Received in revised form

16 April 2008

Accepted 3 May 2008

indicators like the gross domestic product (GDP) due to the

ies. It, the5 thehicho the

were Andalusia (19.7%), Catalonia (14.5%) and the region of

ARTICLE IN PRESS

Contents lists availab

journal homepage: www.else

Building and E

Building and Environment 44 (2009) 584594mental impacts, high-energy consumption, solid waste genera-fax: +34977559667.

E-mail addresses: oscar.ortiz@urv.cat (O. Ortiz), cecile.bonnet@urv.catValencia (13.8%) [3]. In Catalonia, the Catalan Department for theEnvironment and Housing stated that the number of houses builthad increased from 81.786 units in 2002 to 131.517 in 2006 [4]. Onthe other hand, this sector is responsible for adverse environ-

tion, greenhouse gas emissions, external and internal pollution,environmental damage and resource depletion [5].

Corresponding author at: Environmental and Analysis Management Group

(AGA), Department of Chemical Engineering, University of Rovira i Virgili (URV),

Av. dels Pasos Catalans 26, 43007 Tarragona, Spain. Tel.: +34 977559644;

(C. Bonnet), juancarlos.bruno@urv.cat (J.C. Bruno), francesc.castells@urv.cat

(F. Castells).0360-13

doi:10.1sectors high rates of investment and contribution to growth inemployment. Globally, in 2001 this sector represented 10% of

gross value added (GVA). SEOPAN also stated that in 2006 theregions with the highest percentage of housing starts nationwideIn every country the construction industry is currentlyconcerned with improving sustainability indicators [1]. On theone hand, both socially and economically, this sector is highlyindustrially active and can cause uctuations in macroeconomic

the rest of the developed word and 23% in developing countralso employed an estimated 111 million workers [2]. In Spainconstruction industry watchdog (SEOPAN) said that in 200construction industry took a lead growth rate of 6%, waccounted for 17.8% of GDP, and contributed almost 11% t& 2008 Elsevier Ltd. All rights reserved.

1. Introduction global GDP with an annual output of USD 3000 billion, of which30% was in Europe, 22% in the United States, 21% in Japan, 4% inKeywords:

Building life cycle

LCA

Life cycle management

LCM

Residential dwellings

Sustainability indicators23/$ - see front matter & 2008 Elsevier Ltd. A

016/j.buildenv.2008.05.004a b s t r a c t

Life cycle management (LCM) can be applied to the whole construction process, thus making it possible

to improve sustainability indicators and also minimize the environmental loads of the full building life

cycle. To illustrate this, a case study has been carried out based on the application of the LCM approach

to a typical Spanish Mediterranean house located in Barcelona with a total area of 160m2 and a

projected 50-year life span, which has been modeled according to the Spanish building technical code

(CTE). The aim of this research is to use sustainability indicators in the pre-construction and operation

(use and maintenance) phases and also to promote and support the adoption of the LCM within the

construction industry. This paper concludes that regarding the signicant environmental issue of

climate change, there was a total emission of 2.34E03 kg CO2-Eq/m2 per 50 years, of which about 90.5%

was during the operation phase (use 88.9% and maintenance 1.7%) and the pre-construction phase

account for a total of 9.5%. In terms of this dwellings environmental loads, the operation phase is the

most critical because of the high environmental loads from energy consumption for heating, ventilation

and air conditioning (HVAC), lighting, electrical appliances and cooking.

Additionally, the ndings of this study state that the appropriate combination of building materials,

improvement in behaviors and patterns of cultural consumption, and the application of government

codes would enhance decision-making in the construction industry. Therefore, there is no doubt that

applying LCM to the full building life cycle is very important for reducing environmental loads and

thereby improving sustainability indicators. Finally, this research will help develop guidelines based on

LCM for the construction industry to assist stakeholders in improving customer patterns during the

dwelling life cycle.Sustainability based on LCM of residentCatalonia, Spain

Oscar Ortiz a,b,, Cecile Bonnet c, Joan Carles Brunoa Environmental and Analysis Management Group (AGA), Department of Chemical Engll rights reserved.l dwellings: A case study in

Francesc Castells a

ring, University of Rovira i Virgili (URV), Av. dels Pasos Catalans 26,

le at ScienceDirect

vier.com/locate/buildenv

nvironment

ARTICLE IN PRESS

,

mineral wool, insulation brick with interior

EnviTable 1Comparison of LCA studies for residential dwellings

Reference

Specication Blanchard and Reppe

[8]

Asif et al. [9]

Location USA Scotland

Year 1998 2005

Type of residential dwelling Semidetached Semidetached

Usable oor area E228m2 E140m2

Principal building materials Concrete, gravel and

wood

Concrete, timber

ceramics

Wall composition Double 24 studs,with a 8.9 cm spacing

between the inner

wall and outer wall

studs. The wall cavity

is lled with cellulose

insulation

Availability of sustainability

indicators on energy

production

None None

HVAC analysis Yes None

Databases employed DEAM and

Oekoinvenatare fur

Verpackungen

Energy simulation software Energy 10

LCIA approach Based on EPA600/

R-92/245

Life cycle costing Yes None

Application of technical

construction codes

Yes None

Behaviours patterns during

the operation phase

Yes None

O. Ortiz et al. / Building andTo deal with environmental considerations and increasingconcern regarding todays resource depletion life cycle manage-ment (LCM) can be applied to the whole construction process,thus making it possible to improve sustainability indicators andalso reduce the environmental loads of the full building life cycle.Therefore, the application of LCM can be fundamental in pursuingsustainability and improvements in building and construction andimplies the use of the environmental management tool of LCA [6].

Life cycle assessment (LCA) within the construction industry isan important methodology for evaluating buildings from theextraction of raw materials, construction, operation and main-tenance through to nal disposal or demolition (cradle to grave)and also LCA has been gaining attention in the last decade as ameans of evaluating building materials explicitly dedicate toresidential dwellings [7]. For instance, some studies have alreadybeen published on complete LCAs of residential dwellings. One ofthe rst publications evaluated the environmental impacts andenergy use of a residential home in Michigan [8]. Asif et al. [9] alsoapplied an LCA to a dwelling in Scotland. Adalberth et al. [10] hasused an LCA to evaluate four multi-family buildings located inSweden. Peuportier [11] compared three types of house withdifferent specications located in France. Koroneos and Kottas[12] evaluated the annual energy consumption of an existinghouse in Greece. While these studies describe various environ-mental considerations and energy use for residential dwellings inthe USA and some European countries, there is no evidence fromcomparable studies in Spain (see Table 1). The LCA investigationspresented here are not similar. There are differences in the LCAanalyses and in the engineering and physical characteristics. Forexample, it is observed that some studies did not report themethodology used to evaluate the life cycle impact assessment(LCIA). Additionally, there are dissimilarities in the surface ofheated volume, usable oor area, amount of building materialsand energy use during occupation. Also, apart from Koroneos andpolyethylene foil,

gypsum plasterboard

on the inside of the

wall

(polystyrene) insulation

None None Yes

None None None

Danish Oekoinventare

Enorm EQUER HOT 2000

Based on SBIs LCA

tool

CML Ecoindicator 95

None None None

None Yes Yes

None None YesAdalberth et al. [10] Peuportier [11] Koroneos and Kottas

[12]

Sweden France Greece

2000 2000 2005

Multi-family Single-family house Single-family house

700m2 112m2 225m2

Concrete, macadam Concrete blocks Brick

Masonry veneer,

gypsum plasterboard,

Concrete blocks and

8 cm internal

The external wall

consists of double

ronment 44 (2009) 584594 585Kottas, most studies did not show results of the environmentalimpacts of energy production. Therefore, in this study, it has beenapplied LCM approach to a typical Spanish Mediterranean houselocated in Barcelona with a total area of 160m2, split into twostoreys and with a projected 50-year lifespan in order to assist theconstruction industry and also to evaluate environmental burdensat regional level during the full building life cycle. This case studyuses current research to develop guidelines based on LCM andapply sustainability indicators within the construction industry.The aim of this research is to use sustainability indicators in thepre-construction and operation (use and maintenance) phasesand also to support decision-making within the building sector.Finally, the present research can be used by stakeholders such asengineers, architects, building constructors, environmentalistsand LCA advisors as an important point of reference for LCMand energy considerations.

2. LCA as a tool to support LCM

LCA is a methodology used to evaluate environmental loadsthroughout all stages of the building life cycle, from origin (rawmaterials) to end of life (disposal waste) [13]. LCA follows theinternational standard series of ISO 14040. Although there areplenty of valuable sources documenting the technical andpractical details, LCA methodology is based on four essentialssteps: goal and scope, inventory, impact assessment and inter-pretation [14]. First, dening the goal and scope involves deningthe purpose, audiences and system boundaries. Second, analyzingthe inventory includes collecting data regarding all relevantinputs and outputs of energy and mass ow as well as emissionsto air, water and land for each part of the process. This phaseincludes calculating the material and energy input and output of abuilding system. Third, the impact assessment evaluates potential

environmental impacts based on the inventory analysis. Thepurpose of the LCIA phase is to estimate the impact onenvironmental loads and on the resources used in the systemmodeled. It consists of three mandatory elements: selection ofimpact categories, assignment of LCI results (classications), andmodeling of category indicators (characterization). The environ-mental impact caused by the system being studied may beassessed using impact categories, which are already in commonuse or by dening new categories. Categories that may beconsidered more relevant in the building sector are globalwarming potential (GWP), acidication potential, eutrophicationpotential and ozone depletion potential [15,16]. The second stepinvolves choosing category indicators corresponding to the impactcategories. The category indicator is the quantiable representa-tion of an impact category. Carbon dioxide (CO2), methane (CH4),nitrous oxide (N2O), chlorouorocarbons (CFCs), hydro chloro-

oriented methods (end points). The mid-points approach involves

2.1.1. Pre-construction phase

The pre-construction phase processes mainly involve theproduction of materials, which implies the use of naturalresources, energy and water consumption, and therefore solidwaste generation, greenhouse gas emissions, external and internalpollution, environmental damage and resource depletion. The pre-construction phase plays an important role in achieving sustain-able construction and thus minimizing the environmental burdenbefore a dwelling has been built. For example, any variationduring the pre-construction phase would affect the environmentalimpact of the nal product. Other activities in this phase are theproduction, manufacturing and nal disposal of building materi-als, planning costs, client requirements, supply chain manage-ment and transport to the construction site. The dwellinganalyzed in this research, is a typical semidetached Mediterra-nean house located in Barcelona, Spain. The house selected has atotal area of 160m2 with two storeys and is made mainly of brick.Table 2a summarizes the principal engineering characteristics ofthe dwelling studied and Table 2b shows the description of thesystem for walls (interior and exterior), roof (pitched) and oors,which has been modeled according to the Spanish buildingtechnical code (CTE) [18]. During this phase, all the buildingmaterials were transported solely by truck and the distance frommanufacture to the construction site was 50km.

2.1.2. Operation phase

This phase is divided into two stages: use and maintenance.During the use phase, the environmental impact of the building

ARTICLE IN PRESS

cosntsen

ion

te d

tionce.atinoni

vitieg t

, msal

Table 2aSurface distribution of the Spanish residential dwelling

Ground oor usable area (m2) Area of windows (m2)

Corridor+stairs 11.1

O. Ortiz et al. / Building and Environment 44 (2009) 584594586the environmental impacts associated with climate change,acidication, eutrophication, potential photochemical ozone crea-tion and human toxicity and the impacts can be evaluated usingthe CML baseline method (2001), EDIP 97& EDIP 2003 and IMPACT2002+. The end points approach classies ows into variousenvironmental themes, modeling the damage each theme causesto human beings, the natural environment and resources.Ecoindicator 99 and IMPACT 2002+ are methods used in thedamage-oriented method.

Finally the last step in an LCA is the interpretation. This stepmaps the environmental impact, identies the signicant issuesand formulates recommendations.

2.1. Case study: system denitions and boundaries

LCA has been an important tool for evaluating buildingmaterials and component combinations as well as for evaluatingconstruction and edication [17]. From this, the building life cycleis illustrated in Fig. 1. The following sections describe the activitiesand system boundaries for each phase.

Output

Output

Output

Input

Input

Input

Dismantling

Phases for the full dwelling life cycle

Planning requirememanagemconstruct

Extraction of raw Materials

ManufacturingMaterials

Buildingconstruction

Demolition

Operation (owner)

Use andMaintenance

Was

RehabilitamaintenanHVAC: HeAir Conditi

Actidurin

Productionfinal dispo

Pre-construction uorocarbons (HCFCs) and peruorocarbons (PFCs) all fall withinthe GWP category and are related to all the relevant outputs in theLCI results which contribute to GWP through characterizationfactors. The result is a rearranged list of the LCI results in whichthe data concerning different environmental loads (for example,emissions, wastes, use of resources and energy) is sorted underthe different categories. In fact, in a LCIA, there are essentially twomethods: problem-oriented methods (mid-points) and damage-recycling

Fig. 1. Schematic representatioRECYCLING

ts, client , supply chain t, transport to site.

isposal and

, repair, and Service life for g, Ventilating,

ng.

s involved he process

Phases for building materials

anufacturing and of building materials.

Extraction of raw Materials

Manufacturing

Transport

Use

Waste

Total 72.3 19.2

First oor usable area

Bath 2 11.1 1.4

Bedroom 1 19.0 5.2

Bedroom 2 11.5 4.0

Bedroom 3 19.5 5.3

Corridor 11.1 0.9

Total 72.3 17.0Bath 1 11.1 1.4

Dinningliving room 25.3 8.0

Kitchen 13.1 6.5

Hall 11.5 3.1 materials. management

n of the building life cycle.

maairapp

opsim

int

operation phase, the following parameters have been considered:

span of the dwelling there must be some refurbishing activities.These processes are concerned to the replacement of all ooring,quarry tiles, and replacement of all windows and external doors.

ARTICLE IN PRESS

Pitc

Combined cycle24%

Nuclear22%

Pumped storage hydroelectric

1%

Hydroelectric9%

Coal26%

Gas5%

Oil4%

Other1%

Wind8%

Fig. 2. Spains total electricity mix production.

Envi Number of occupants in the home (4 persons 2.00E02pers/m2).

Heating and cooling setpoints in the different rooms arepresented in Table 3. The dwelling has a split system with acoefcient of performance (COP) of 2.35 for heating and 1.85for cooling.

Daily domestic hot water consumption (DHW). This has beenestimated at 3.00E01 l/pers/day at a temperature of 60 1C.DHW is produced by an electrical heater with an estimated95% efciency.

I[21mumienecyc

acccontocomerface for the EnergyPlus thermal simulation engine [20].To evaluate the buildings energy consumption during thetypThe annual energy consumption of the house during theeration phase has been evaluated using the building energyulation software DesignBuilder [19] and by taking into accountical weather conditions for Barcelona. DesignBuilder is a userthoinly results from energy consumption for heating, ventilation,conditioning (HVAC), domestic hot water, lighting, electricalliances and cooking. Other environmental impacts such asse due to wastewater will not be considered.und oor Ceramic 4.5Firs

Grot oor Wooding ooring 6.5hed roof Clay tile 50.0

MW stone wool 2.8

Roong felt 4.8Table 2bDescription of systems

System Characteristics

Materials (kg/m2)

External walls Polyethylene (4 cm) 1.2

Cement 5.9

Water 2.7

Sand 20.6

Internal walls Gypsum plastering 12.3

Brickwork 165.5

O. Ortiz et al. / Building andAnnual energy consumption for cooking. This is estimated at2.50E02kWh/pers a (electrical cooking).Annual energy consumption for other electrical appliances.This is estimated at 1.20E01kWh/m2.Annual energy consumption for lighting. Table 4 shows therequired lighting level in the different rooms and the lightingpower which has been installed. This is estimated at about1.60E01kWh/m2 a.The total annual electricity consumption of the dwelling hasbeen evaluated at 1.22E04 kWh/a corresponding to almost7.65E01 kWh/m2a.

n 2006, Spains total electricity production was 2.68E05GWh]. Fig. 2 illustrates how this electricity was generated and howch electricity each different technology contributed to the totalx. In the present case study, it has been assumed that thergy supply will remain constant during the buildings lifele.Finally, regarding the maintenance phase, this part takes intoount the activities needed to keep the dwelling in gooddition during the occupation phase. These activities are relatedrepainting, reroong, replacing the cooker and changing allpact orescent light bulbs. Moreover, during the 50-year lifeTable 3Main characteristics of the operation phase

Environmental control

Dinning

room

Kitchen Bath Bedrooms Corridor+stair

Temperature for heating 21 18 22 18 18

Temperature for

ventilation

25 27 24 25 25

Table 4Level of illumination required for the dwelling

Level of illumination required Lux

Kitchen 300

Dinningliving room 150

Bath 1 150

Corridor+stairs 100

Bedrooms 100

Potential illumination installed 3.4W/m2. 100 lux

Electricity composition in Spainbased on 268799 GWh / year (2006)

ronment 44 (2009) 584594 5872.1.3. Dismantling phase

The dismantling phase often results in landll disposal orrecycling of the majority of materials such as concrete, wood,drywall and metal. Due to the lack of data on materials recovery,we have not taken into account the dismantling phase. Never-theless, of the buildings whole life cycle, the dismantling step isnot usually signicant because most of the environmental effectsare generated during the operation phase [22].

2.2. Limitations

There are some uncertainties and limitations to the presentwork. First, Pushkar et al. [23] stated that construction as aprocess is not static; it varies from building to building since eachhas its own function and different engineering characteristics.Gregory and Yost [24] concluded that the direct application of LCAin the construction sector is not a simple or straightforwardprocess. It is expensive and cannot be applied without makingassumptions or additional modications. Consequently, variationin each design can affect the environment during all life cyclestages for a building. Paulsen and Borg [25] declared thatbuildings and building materials are characterized by theirsignicantly longer life compared to most other industrial

2001 method provides operational guidelines for conducting an

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pote

Chloroform (air) 3.00E01

n by technology at the busbar Transportation Total

Categorization of the impacts presented in the ecoprole for the dwelling life cycle

studied

Environmental impact Equivalent

ecoprole

Unit

Acidication potential 1.85E01 kg SO2-Eq/m2 per 50years

Human toxicity 7.18E02 kg1.4-DCB-Eq/m2 per 50years

Depletion of abiotic

resources

1.72E01 kg antimony-Eq/m2 per

50years

Climate change 2.34E03 kgCO2-Eq/m2 per 50years

Terrestrial ecotoxicity 6.82E01 kg1.4-DCB-Eq/m2 per 50yearsStratospheric ozone

depletion

1.17E04 kgCFC-11-Eq/m2 per 50years

nviproducts, and the involvement of many different factors duringtheir life cycle.

Second, a key issue for the present work is the quality andapplicability of data contained in the system. For instance,Frischknecht et al. [26] found that consistent, coherent andtransparent LCA datasets for basic processes make it easier tocarry out LCA projects and thereby increase the credibility andacceptance of the LCA results. As far as LCA methodology isconcerned, some of its tools are available for environmentalassessment. These tools have been steadily improving and havebeen classied according to three levels. Level 3 is called Wholebuilding assessment framework or systems; level 2 is calledWhole building design decision or decision support tools. Level1 is for product comparison. Some of the databases used forenvironmental evaluation are: CML, DEAM TM, Ecoinvent Data,

Carbon oxide CO (air) 1.53E00

Table 6Environmental impacts of the nal Spanish electricity mix (based on 1kWh)

Environmental impact Electricity productio

Acidication (kg SO2) 3.53E03Human toxicity (kg 1.4-DCB-Eq) 5.02E02Depletion of abiotic resources (kg antimony-Eq) 3.51E03Climate change (kgCO2-Eq) 4.53E01Terrestrial ecotoxicity (kg 1.4-DCB-Eq) 7.19E05Stratospheric ozone depletion (kgCFC-11-Eq) 2.30E08Table 5Classication of some environmental impacts on climate change and acidication

Climate change GWP 100GLO kgCO2 Eqv.

Carbon dioxide, fossil CO2 (air) 1.00E00

Methane, fossil CH4 (air) 2.30E01

Dinitrogen monoxide (air) 2.96E02

Sulphur hexauoride (air) 2.22E04

O. Ortiz et al. / Building and E588GaBi 4 Professional, IO-database for Denmark 1999, Simapro, theBoustead Model 5.0 and the US Life cycle inventory [27].Nevertheless, those tools and database vary according to users,application, data, geographical position and scope. Besides,because of continuing data limitations, and the large range ofconstruction techniques and materials, none of these tools iscurrently capable of modeling an entire building, or computingthe environmental impact of all life cycle phases and processes[28]. As a result, to deal with the LCI analysis, the impactassessment and interpretation, the results of this research werepresented in Ecopoints and were developed with the support ofLCA Software called LCA-Managers developed by SIMPPLE (spinout of the URV). Finally, the present project used processesinventoried in the Ecoinvent Database V1.3 in order to providegeneric background data of products and processes [29].

2.3. Methodology and application

Determining the functional unit (FU) is crucial when evaluat-ing the goal and scope of LCA for residential buildings. Hence, thepresent work is based on the m2 usable oor area of a dwellingwith a projected 50-year life span and four people living inthe house. The impact assessment in this project is based uponthe CML 2 method (2001) developed by Leiden Universitys Centerfor Environmental Science due to its broad international accep-tance and its common application in the building sector. The CML1.00E03 4.53E038.00E02 1.30E016.00E04 4.11E039.00E02 5.43E017.00E05 1.42E043.00E09 2.60E08

Table 7ntial

Acidication potential genericGLO kg SO2 Eqv.

Ammonia NH3 (air) 1.88E00

Nitrogen dioxide (air) 7.00E01Sulphur dioxide (air) 1.00E00

ronment 44 (2009) 584594LCA study step by step on the ISO standards. The CML 2001method is a midpoint approach, which covers all emissions, andresource-related impacts. In the present case study, we choseclimate change, acidication potential, human toxicity, depletionof abiotic resources, terrestrial ecotoxicity and stratospheric ozonedepletion in order to assess the environmental impacts. Thesubcategories for some of the environmental impacts studied areindicated in Table 5.

3. Life cycle assessment: results

We have paid particular attention to input variables inelectricity consumption. Therefore, the environmental impactsof the electricity consumption has been evaluated based on theEcoinvent database adapted to the Spanish electricity mix for2006 and it is out the scope the power plants self, losses andimports [30]. Table 6 summarizes the nal environmental impactsbased on 1kWh including the shares of domestic electricityproduction by the technologies at the busbar. It also includes thetransmission, transformation and distribution processes (calledtransportation).

Next, the LCA results of the full dwelling life cycle will bepresented rst, followed by a sensitivity analysis across thebuilding life cycle system.

Table 7 shows the total ecoprole for the building life cycleanalyzed.

The present case study has dealt particularly with climatechange because of its importance within the constructionindustry both globally and locally and because it is an environ-mental impact that affects the whole planet [31,32]. Therefore, we

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t 6

l im

-50

0

50

100

150

kg C

O2

eq/m Polyvinylchloride

Brick

Steel

Concrete

Timber

Fig. 4. Global warming potential of 1m2 usable oor area for six buildingmaterials.

EnviFig. 3 shows how the life cycle environmental impact isdistributed over six categories: acidication potential, humantoxicity, depletion of abiotic resources, climate change, terrestrialecotoxicity and stratospheric ozone depletion. As can be seen inFig. 3, the time phase with the highest environmental impact isthe operation phase; approximately 8092% of the life cyclestotal, except for the human toxicity impact, of which the useaccounts for approximately 70% and the maintenance andrefurbishing activities contributed up to 25% mainly due to thereplacement of all windows. Regarding the environmental issue ofterrestrial ecotoxicity, there was a total emission of 6.82E01kg1.4DCBEq/m2 per 50 years, of which about 18.5% was during thepre-construction phase due to the use of steel and the operationphase accounts for 82%.

The present work has also studied 12 different buildingmaterials in the pre-construction phase. Asif et al. [9] studiedeight construction materials for a dwelling home in Scotland.These materials were timber, concrete, glass, aluminum, slate,ceramics tiles, plasterboard, damp course and mortar. The studyconcluded that concrete had the highest embodied energy in thehouse at 61%. Two other materials, timber and ceramic tiles

0%10%20%30%40%50%60%70%80%90%

100%

Preconstruction TransporAcidification PotentialHuman ToxicityDepletion of abiotic resources

3

1 2 3 4 5 6 1 2 3 4 5

1

5

Fig. 3. Distribution of the environmenta

O. Ortiz et al. / Building andrepresented 14% and 15% of the total of embodied energy,respectively. Concrete was the material responsible for 99% ofthe total of CO2 during the homes construction. This supports theresults in Fig. 4. This graph depicts that the dwelling had positiveand negative values. Positive values mean net CO2 emissions tothe environment while negative values represent a credit of CO2due to carbon xation in wood. Nevertheless, there is no doubtthat using timber is indispensable in reducing environmentalimpacts such as CO2, although some authors have stated thatgiving a negative GWP to wood is incorrect, because the wood willsooner or later be incinerated or land lled, resulting in a neutralor positive CO2 balance [11].

Furthermore, Fig. 4 also shows that the pre-construction phaseaccounts for 1.96E02kg CO2-Eq/m

2 with the resulting effect onglobal warming. This is due to a large number of different buildingmaterials, of which both concrete and steel make up 77.22% andbrick accounts for 14.68% of the total, respectively. These resultsshow that the pre-construction phase has a strong inuence forselecting sustainable materials with low environmental burdensand good insulation properties. Therefore, even if the contributionof the building materials themselves is low compared with valuesof the whole life cycle, choosing them carefully, together with anappropriate design of the building structure and orientation, canlead to important energy savings in the operation phase. Use MaintenanceClimate changeTerrestrial EcotoxicityStratospheric Ozone Depletion

4

1 2 3 4 5 6 1 2 3 4 5 6

2

6

pacts of the dwelling life cycle studied.

200

250

2Roof tileronment 44 (2009) 584594 589did comparative LCA analyses of single buildings to assess theenvironmental impact during the operation cycle. For instance,Blanchard and Reppe [8] analyzed the total life cycle energyconsumption and the GWP of a standard home of 227.8m2. Thelife cycle GWP was 1.01E06 kg CO2. Adalberth et al. [10] evaluatedthe life cycle of four dwellings located in Sweden with differentconstruction characteristics. The results concluded that GWP wasapproximately 1.5 tons CO2 equivalents/(m

2 per 50 years) for allbuildings. Peuportier [11] compared three types of house withdifferent specications located in France and results showed thatthe amount of CO2-Eq/m

2 emitted during their 50-year life cyclewas approximately 2.10E03kg. Finally, in the present researchanalysis on evaluating the signicant environmental issue of climatechange, there was a total emission of 2.34E03kgCO2-Eq/m

2 per50 years, of which about 90.5% was during the operation phase(use and maintenance); while pre-construction contributed up to8.4% and transport accounts for 1.1%.

4. Sensitivity analysis

This paper focuses on a sensitivity analysis based on threeinitiatives during the full building life cycle. These alternatives aregiven by real scenarios, whose purpose is to model how the input

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e

nviTable 8Reference house and alternatives versus requirements in the CTE

System U-values (W/m2K)

(reference house)

Alternative 1 U-values

(W/m2K)

Wall 0.38 0.60

Roof 0.40 0.40

Floor 0.48 0.48

Windows

North 3.22 3.22

W/E 3.22 3.22

South 3.22 3.22

Table 9Effect of using window blinds

Case Reference hous

Energy demand for heating (kWh/m2a) 2.09E03

Energy demand for cooling (kWh/m2 a) 5.97E03

Energy savingsheating (%)

Energy savingscooling (%)

Energy savingsheating+cooling (%)

O. Ortiz et al. / Building and E590data affects the output data in a small but realistic productsystem. To accomplish this, it has been taken into account thelegal requirements of directive 2002/91/EC of the EuropeanParliament, which in turn promote the energy performance ofbuildings based on the Spanish building technical code (CTE), theregulation of thermal installations (RITE) [33] and the energyefciency certication of buildings [34].

This part also addresses the question of whether there is anenvironmental advantage in using Material A instead of MaterialB, and compares the typical dwelling (reference house) with threealternatives.

Regarding the heat transfer coefcient (U-values) of thereference house, the limit values given by the aforementionedCTE code have been taken into account. Table 8 presents theU-values used in this study.

The rst alternative was to vary the insulation of the externalwalls using 8 cm thick expanded polystyrene instead of 4 cm. Afterthe sensitivity analysis had been completed, the results showed a2.02% increase in the overall greenhouse gas emissions during thepre-construction phase, due to increased quantities of materials,but there is a reduction of 1.83E01 kg de CO2-Eq (m

2 per 50 years)because the energy demand for heating decreases by 20.7%.

In the second alternative, window blinds are evaluated. In thiscase, user behavior regarding the blinds is also taken into account.These are aluminum blinds with medium reectivity slats locatedon the outside of the windows. Alternative 2a represents a passiveuser where blinds are always closed. This means that they reducethe solar heat gains in summer but also in winter, leading to asignicant reduction in the cooling demand but also a major

Table 10Variations in the windows characteristics

Reference house Alternative 3

Outside pane Clear 3mm Clear 4mm glass

Air gap Air gap Air gap 12mm

Inside pane Clear 3mm Low-emissivity 4mm glassincrease in the heating demand in winter. In alternative 2b userbehavior is optimal. Blinds are inside and are closed during thenight if there is a heating demand and open during the day if thereis a cooling demand. This reduces the cooling demand in summerby reducing solar gains and reduces heat losses through thewindows at the night during the winter. Values of energy demandin alternatives 2a and 2b are presented in Table 9.

Finally, in the third alternative, windows with low-emissivityglass were used instead of clear 3mm glass (reference house) onthe internal side of the window, as shown in Table 10.

As a result, windows with low-emissivity glass have a lower

Alternative 2 U-values

(W/m2K)

Alternative 3 U-values

(W/m2K)

U-values limit CTE

(W/m2K)

0.38 0.38 0.73

0.40 0.40 0.41

0.48 0.48 0.50

3.22 2.06 3.40

3.22 2.06 3.90

3.22 2.06 4.40

Alternative 2a Alternative 2b

2.04E03 2.19E03

4.00E03 5.73E03

2.0% 5.0%33.1% 4.0%

25.1% 1.7%

ronment 44 (2009) 584594heat transfer coefcient (U-value) than the conventional windowsof the reference house, reducing the energy demand of thebuilding for heating and cooling by 2.2% and 3.1% respectively, andleading to a reduction in the corresponding CO2-Eq emissions of2.05 kg of CO2-Eq (m

2 per 50 years).Nevertheless, the environmental impact of GWP in kg of

CO2-Eq per 1m2 for the construction phase has been measured for

the three alternatives considered. Results are presented in Fig. 5.As can be seen in Fig. 5, alternative 2 had a signicant increase

in total PFCs of about 150% due to the production of aluminum forthe blinds. Even if this alternative presents a relatively high valueof CO2-Eq when compared to the reference value, it is demon-strated that it is the best alternative because of its high-energysavings during the operation phase. In addition, this study hasevaluated the effect of the full dwelling life cycle on climatechange. Therefore, it can be observed that in all the optionsthe most signicant impact comes from the operation phase(see Fig. 6).

Finally, Fig. 7 shows how the impact of household energy in thereference house is distributed. Heating and cooling representabout 34% of the total equivalent CO2 emissions. The applicationof alternatives 2a could reduce this impact to about 9% CO2-Eq/m

2

per year. These results demonstrate the importance of usingappropriate building design practices for energy saving during theoperation phase. Nevertheless, it is obvious that this type of actionmust be accompanied by changes in behaviors patterns on thepart of the user to reduce the remaining part of the householdenergy, and not depend on the building design. In the next sectionthis aspect is further developed.

mention some LCM initiatives in the distribution of buildingsconthatsust

I

ARTICLE IN PRESS

ive

dwel

Envi180

185

190

195

200

Reference house Alternat

kg C

O2

Eq/m

2

Total Carbon DioxideTotal perfluorocarbons (PFCs)Total dinitrogen monoxideTotal hydrofluorocarbons HFCs

Fig. 5. Greenhouse gas emissions of the

Alternative 2a

Alternative 2b

Alternative 3

O. Ortiz et al. / Building and5. Life cycle management: initiatives to improve sustainabilitywithin the construction industry

LCM can be applied to the whole construction process, thusmaking it possible to improve sustainability indicators. Forexample, a proper design and choice of building materials duringthe pre-construction phases can improve the energy efciencyduring the operation phase and the nal distribution of buildingsconsumption for heating and cooling. Also applying strategiesduring the operation phase, such as making changes in consump-tion patterns, would improve consumption for illumination andhousehold equipment in terms of energy and environmentalconsiderations. Therefore, patterns of consumption have beenspecically dealt within this paper. This has meant governmentpolicies have been applied to reduce the nal energy demand andenvironmental impacts without compromising quality and thehealthy indoor environment for users. The activities that areinvolved during the operation phase may include direct andindirect patterns. For instance, direct patterns may relate toenergy consumption resulting from leaving blinds open. Indirectpatterns may include the whole process of producing, transmit-ting, transforming and distributing the electricity needed to meetthe energy consumption of every Spanish household.

Fig. 8 shows the nal distribution in the dwelling studied.Lighting represents a signicant 21% of the total for the fulldwelling energy consumption, while cooling and heating accountfor 33%, domestic hot water accounts for 21% and house

theenethis

energy needs for bedrooms is estimated at 10W/m2 and living

0 500 1000 1500 2000 2500

Reference house

Alternative 1

kg CO2 - eq / m2

Preconstruction TransportUse Maintenance

Fig. 6. Incidence of the dwelling life cycle phases of the climate change.rooms, and at 20W/m2 for kitchens, using incandescentlamps. If uorescent lamps are used then the energyrequirements are 45W/m2 in bedrooms and 710W/m2 inkitchens. It is estimated that installing suitable lightingthroughout the dwelling will cost approximately 100h.However, the resulting savings are estimated at 10% of theannual lighting energy consumption.

For cooling and heating, combining building products and(b)comalmHowinveheabederaHerof 2

Csusteneconmentherstrablinreduof 1whirefewhenever not strictly needed. Together these alternatives willbe lead to an overall reduction of 15% of the nal annualenergy consumption.Lighting equipment: Install sensors at indoor and outdoor sitesand use suitable lighting throughout the dwelling; lighting(a)sumption for the reference house and also some of the mattersshould be taken into account when trying to improve

ainability indicators for residential dwellings.llumination is strictly dependent on consumption behavior, soreduction and initiatives taken could only be in the area ofrgy efciency. Some of the following are proposals to achieve.

Lighting: use sunlight as much as possible and turn off lightsequipment and cooking account for 25%. In this section, we

1Alternative 2Alternative 3

Total MethaneTotal Carbon MonoxideTotal halocarbons

lings during the pre-construction phase.

ronment 44 (2009) 584594 591ponents for insulation can reduce environmental loads byost 1.83E01 kgCO2-Eq/m

2 per year during the use phase.ever, in order to achieve this, the owner faces an additionalstment cost of about 4800h. Regarding energy savings,ting would have a positive balance, while cooling wouldnegative. Other aspects that have been taken into consi-tion are the use of windows with low-emissivity glass.e, heating and cooling accounted for a total energy saving.9%.onsumption patterns play an important role in savings andainability indicators in the use phase for every aspect ofrgy consumption. For example, good patterns of use bysumers and users are indispensable for reducing environ-tal impacts. The advantage of changing users behavior is thate is no additional cost for this strategy. Energy savingtegies are, for example, not leaving windows open and usingds correctly and could lead to energy consumption beingced by up to 25.1% and 1.7% respectively, and save an average.06E02 kgCO2-Eq/m

2 per 50 years in environmental loads,ch represents a savings of 5% in relation to the impact of therence house (see Table 11).

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0

4

8

12

16

nvi0

5

10

15

20

25

30

35

40

45Household energy use for the reference house

kg C

O2e

q/(m

2 pe

r yr)

kg C

O2e

q/(m

2 pe

r yr)

Air Conditioning Heating Hot water sanitary

O. Ortiz et al. / Building and E5926. Discussion and outlook

The principal environmental considerations for the full dwell-ing life cycle based on LCM were to evaluate building materialsthat were more efcient in terms of their environmental burdenand to evaluate the impact of energy consumption during theoperation phase. Regarding electrical appliances, the most recentmethodologies which incorporate information about environ-mental aspects, embodied energy and efciency are necessary forsustainable development. To achieve this, the European Commis-sion ofcially released the European energy label which ratesproducts from A (the most efcient) to G (the least efcient) [35].

Nevertheless, decision-making regarding any environmentalimpact depends on global and local environmental quality goalsand also on environmental threats identied in research anddevelopment by governments. Governments need to applypolicies and construction codes that lead to improved quality oflife for citizens because these same citizens want assurances thatan investment in a dwelling will pay for itself over an acceptabletime period. In other words, cost is an important issue for themarket in facilitating the best economic and ecological value forsociety, customers and users.

Fig. 7. Household energy consumption for

Distribution of dwelling's consumption for the reference house

Cooking9%

Heating7%

Illumination21%

Hot water sanitary21%

Cooling26%

Household equipment16%

Fig. 8. Distribution of the reference houses consumption.The present case study has shown that the combination ofbuilding materials can lead to reduced environmental impacts.There is a widespread desire to reduce Spanish CO2 emissions,therefore decisions need to be made with rigorous and appro-priate environmental goals set out by the government. This workevaluated and analyzed adverse environmental impacts duringthe pre-construction and operation phases. LCM has been used indecision-making when applying the environmental managementprinciple of choose it right rst without compromising thequality of a construction project. Hence, this allowed us to see andevaluate environmental burdens based on combinations ofdifferent building materials. Finally, future work in this projectwill cover aspects of sustainability indicators due to changes inthe dwelling energy sources (renewable versus non renewable)and variance in the energy efciency of electro-domestic equip-ment and also will consider the construction and demolitionwaste, and will analyze whether the practical LCM guidelines usedComparative of the heating and air conditioning(reference house versus alternatives)

Illumination Household equipment Cooking

Referencehouse

Alternative1

Alternative2a

Alternative2b

Alternative3

the reference house and alternatives.

ronment 44 (2009) 584594in the Spanish sector can be applied in other regions and countries.

7. Conclusions

LCM plays an important role within the Spanish building sectorin helping decision-making in order to optimize sustainabilityindicators. There is no doubt that applying LCM to residentialdwellings can be very important for achieving sustainabledevelopment. Due to its broad international acceptance, LCMshould not be used for improving processes and services, butrather it should be seen as an approach for enhancing quality oflife so that people can live in a healthy environment, and forimproving social, economic and environmental conditions in bothdeveloped and developing countries.

This research concludes that in the whole construction process,the operation phase is the most critical because of the higherenvironmental burden emitted into the atmosphere.For example,regarding the signicant environmental issue of climate change,there was a total emission of 2.34E03kgCO2-Eq/m

2 per 50 years,of which about 90.5% was during the operation phase.

Finally, this work has demonstrated that using LCM initiativeson consumption behaviors during the full building life cyclewould help to enhance energy, economic and environmentalsavings, which would in turn accomplish building sector sustain-ability and promote the use of sustainable construction practices.

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rgy

h/FU

b SH

SH

SH

0b S

a

0a

a

latio

: do

EnviTable 11LCM initiatives of residential dwellings within the Spanish building sector

Phase Aspect Normal behaviour

reference house

Proposed behaviour Ene

kW

PC IS D External walls using

4 cm thick expanded

polystyrene

External walls using

8 cm thick expanded

polystyrene

20.7

PC IS D Clear glass on the

internal side of the

window

Windows with low-

emissivity glass

2.2b

U UB D Leaving windows

open carelessly

Taking care to close

windows

2.0b

U USH D Aluminium window

blinds with medium

reectivity slats

located on the outside

of the windows

Blinds are closed

during the night if

there is a heating

demand and open

during the day if there

is a cooling demand

5.

U E IN Electrical cooker Gas cooker 450

U DHW IN Electrical heater Boiler of natural gas 22M R D Cooker: dirty or

clogged orice

Clean burner orice 100

M IL D Illumination not

adequate

Proper illumination 80a

Abbreviations: P: pre-construction, U: use, M: maintenance, C: construction, IS: insu

of solar heating, UB: user behaviour, R: repairs, a: measured in kWh electric, DHW

heating demand, SCD: saving cooling demand.

O. Ortiz et al. / Building andAcknowledgments

This project is part of the collective arrangement between theRovira i Virgili University (URV), Spain and the University ofPamplona, Colombia. Helpful feedback was provided by JulioRodrigo (SIMPPLE-spin out of the URV). Finally, part of this workhas been presented in the 3rd Life cycle management confer-enceLCM 2007. Zurich, August 29, 2007.

References

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[9] Asif M, Muneer T, Kelley R. Life cycle assessment: a case study of a dwellinghome in Scotland. Building Environ 2005. 11.023.

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D 2.3b SCD 3.6 90 4800 1.83E01

D 3.1b SCD 2.9 60 10,141 2.05E01

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HD 4.0b SCD 1.7 30 0 1.46E01

42.2 60 700 5.75E03

8.5 140 1200 3.07E049.4 8 0 9.50E02

3.1 10 100 2.30E03

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construction: a state of the art report. Published by the Society ofEnvironmental Toxicology and Chemistry (SETAC). 2003. ISBN:1880611597.

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O. Ortiz et al. / Building and Environment 44 (2009) 584594594

Sustainability based on LCM of residential dwellings: A case study in Catalonia, SpainIntroductionLCA as a tool to support LCMCase study: system definitions and boundariesPre-construction phaseOperation phaseDismantling phase

LimitationsMethodology and application

Life cycle assessment: resultsSensitivity analysisLife cycle management: initiatives to improve sustainability within the construction industryDiscussion and outlookConclusionsAcknowledgmentsReferences